This invention relates to steam generators and in particular to large units with combustion being carried out in a fluidized bed.
Small steam generators are bottom supported. This is the simplest construction with the entire unit being posted from the bottom support. Such a design is impractical however, for a large steam generator because of the great height, high loads and significant expansion. These large steam generators are therefore top supported from building steel with the unit expanding downwardly.
When a fluidized bed is used for combustion in a large steam generator, it imposes extremely high loads on the unit. This makes top support of the entire unit difficult. It therefore, is desirable to combine both bottom and top support by including an expansion joint within the unit. This is illustrated in a technical paper by Joseph R. Comparato entitled "C-E Power System Filled Design Development for the TVA 200-MW Atmospheric Fluidized Bed Combustion Demonstration Plant" presented at the seventh international conference on fluidized bed combustion, Oct. 25-27, 1982. U.S. Pat. No. 3,208,436 issued to R. L. Godchaulk illustrates a large steam generator with expansion joints in the water walls.
These prior art joints must be designed for high temperature which leads to questionable reliability and susceptibility to plugging from solids in the combustion products.